Add examples

[safareli]

• list examples from other Free libraries to port them

[safareli]

https://github.com/DrBoolean/freeky https://github.com/fantasyland/fantasy-frees/tree/master/examples http://www.haskellforall.com/2012/07/purify-code-using-free-monads.html https://www.chrisstucchio.com/blog/2015/free_monads_in_scalaz.html http://underscore.io/blog/posts/2015/04/14/free-monads-are-simple.html http://okmij.org/ftp/Computation/free-monad.html https://github.com/typelevel/cats/blob/master/docs/src/main/tut/freemonad.md https://hackage.haskell.org/package/free-4.12.4/docs/examples/ValidationForm.hs https://hackage.haskell.org/package/free-4.12.4/docs/examples/RetryTH.hs https://hackage.haskell.org/package/free-4.12.4/docs/examples/Teletype.lhs http://typelevel.org/cats/datatypes/freemonad.html http://typelevel.org/cats/datatypes/freeapplicative.html https://gist.github.com/safareli/b43f43d3e65483b71b08b894386f4d71 http://clathomasprime.github.io/hask/freeDecision https://jaspervdj.be/posts/2012-09-07-applicative-bidirectional-serialization-combinators.html http://www.paolocapriotti.com/blog/2012/04/27/applicative-option-parser/ https://github.com/Avaq/momi using Free https://github.com/markus1189/flatmap-oslo-2016/ https://github.com/aecor/liberator https://github.com/47deg/freestyle https://github.com/HeinrichApfelmus/operational/tree/master/doc/examples